Contextual Filter Modification for URL

I'm attempting to access a field for a contextual filter and want to modify it by replacing white spaces with dashes and converting to lower case. This option is visible for title, but not another field that I want to use. Is there a way to do this, either through the interface or programmatically?

In particular, I am using OG (organic groups) and want to compare the audience of a group content item to the title of a group (using panels to compile the information onto one page and want to keep simple URLs, hence using the group name over an identification number).